In the documentation about affinity and anti-affinity rules for kubernetes there is a pratical use case arround a web application and a local redis cache.

1. The redis deployment has PodAntiAffinity configured to ensure the scheduler does not co-locate replicas on a single node.
2. The webapplication deployment has a pod affinity to ensure the app is scheduled with the pod that has label store (Redis).

To connect to the redis from the webapp we would have to define a service.

Question: How are we sure that the webapp will always use the redis that is co-located on the same node and not another one? If I read the version compatibility from Kubernetes v1.2 the iptables mode for kube-proxy became the default.

Reading the docs about iptable mode for kube-proxy it says by default, kube-proxy in iptables mode chooses a backend at random.

So my answer to the question would be: No we can't be sure. If you want to be sure then put the redis and webapp in one pod?